Hi,
I have set my isolated footing design to remain in full contact with the soil. However, when I check the eccentricity of the factored loads, it is beyond the kern which is 1/6 of the footing dimension.
1) Why does SFA give out such design when this kind of footing design is unacceptable?
2) Given that the eccentricity is beyond the kern, does this mean that my footing is experiencing loss of contact?
8030.Isolated Footing - Axial.sfa
Eccentricity larger than kern distance means there will be loss of contact.
There is an error in your calculation. The FY in the screenshot you attached consists only of the load acting through the column (144 kN). For load combination 5, you need to add the factored value of selfweight of the footing plus the weight of soil = 1.2*(11.747 + 30.636) = 50.8596 kN. That will increase the total vertical load to 144 + 50.8596 = 195 kN, which will cause the eccentricity to come down (40/195 = 0.205 which is smaller than the kern distance).
Answer Verified By: Louis Flores